1. Field of the Invention
The invention is directed to an improved adjusting device for adjusting the position of a final control element using a transmission.
2. Description of the Prior Art
There are known adjusting devices for internal combustion engines in which a servomotor must move a final control element via a transmission. For example, the final control element is a throttle valve flap. Because there is frequently very little room available for the adjusting device in a motor vehicle, it is necessary to keep its size to a minimum. In order for a relatively small servomotor to be able to move the final control element quickly and precisely, a transmission is provided between the servomotor and the final control element. Due to the limited amount of available space, the transmission must be as small as possible.
DE 195 25 510 A1 and U.S. Pat. No. 5,672,818 have disclosed an adjusting device provided in the intake manifold of an internal combustion engine. The adjusting device disclosed therein has a throttle valve shaft that is supported in a throttle valve housing in pivoting fashion and has a throttle valve flap attached to it. The throttle valve housing has a gas duct passing through it. The throttle valve flap opens or closes the gas duct in response to the pivoting of the throttle valve shaft. A servomotor can move the throttle valve flap via a transmission. The transmission is situated in a transmission housing and has a number of gears. A middle gear is supported in rotary fashion on an axle that is attached to the main body of the throttle valve housing. The transmission housing is covered by a cover. Because the cover has, among other things, parts of a position sensor attached to it, the cover must be positioned very precisely in the region of the position sensor. For this reason and due to production tolerances that can never be entirely avoided, there is necessarily play, particularly in the radial direction, in the region between the cover and the end of the axle oriented toward the cover. For this reason, the axle can only be secured in the region of the main body, whereas in the region of the cover, it is only possible for it to be supported loosely, with a large amount of play. This has the disadvantage that the axle, particularly at the point at which the axle comes out of the main body, is loaded with a large amount of bending stresses and shearing stresses and that a particularly high-strength material must therefore be used for the axle or else the axle would have to be so thick that it would require the entire device to be unnecessarily large.